Twin wire former

ABSTRACT

The invention relates to a twin wire former ( 1 ) for producing a fibrous web ( 4 ), in particular a paper, cardboard or tissue web, from a fibrous suspension according to the generic terms claim 1. The twin wire former ( 1 ) is characterized in that, the two wire belts ( 2, 3 ) run upwards after a passing a first deviation device ( 10 ), forming an angle (β) relative to an imaginary second horizontal plane (H2), in such a way that the upper vertex ( 15 .SO) of the second deviation device ( 15 ) lies above the lower vertex ( 10 .SU) of the first deviation device ( 10 ), and that the angle (δ) relative to the imaginary first horizontal plane (H1) runs downwards.

[0001] The invention relates to a twin-wire former for producing afibrous web, in particular a paper, board or tissue web, from a fibroussuspension according to the preamble of claim 1.

[0002] A twin-wire former of this type is known from the GermanPublished Specification DE 198 03 591 A1 (PB10656 DE) from theApplicant. The twin-wire former has two wire belts (lower wire and upperwire), which together form a twin-wire zone. In a first part of thetwin-wire zone, in which the two wire belts run over a dewateringelement in the form of a rotating forming roll, the two wire beltstogether form, directly at the forming roll, a wedge-like inlet gap,which picks up the fibrous stock suspension directly from a flowbox(“gap former”). In a second section of the twin-wire zone, the two wirebelts with the fibrous web forming between them run steeply downwardover further dewatering elements, for example over a plurality offorming foils and/or at least one forming shoe, preferably at an angleof 10° to 60° relative to an imaginary vertical plane. At the end of thesecond section of the twin-wire zone, the wire belts run over adeflection device and then over a separating device, which separates oneof the wire belts from the forming fibrous web and from the other wirebelt.

[0003] The disadvantage with this known twin-wire former is that,because of the relatively great forming roll diameter, which car assumea value for example between 1.5 and 2.5 m, it has a very large overallheight. This large overall height leads to problems with regard to theheight of the hall or crane, particularly in the case of rebuilds, andtherefore to increased rebuilding costs and overhaul or operating costs.

[0004] It is therefore an object of the invention to improve a twin-wireformer of the type mentioned at the beginning in such a way that theoverall height is reduced such that, during rebuilds, no significantadditional costs (rebuilding costs, overhaul costs, operating costs)arise and that, at relatively high machine speeds, complete secondarydewatering is made possible.

[0005] In the case of a first twin-wire former of the type mentioned atthe beginning, this object is achieved, according to the invention, inthat after the first deflection device, the two wire belts run upward atan angle relative to an imaginary second horizontal plane, in that theupper vertex of the second deflection device is located above the lowervertex of the first deflection device, and in that the angle between theflowbox and the imaginary first horizontal plane runs downward.

[0006] This achieves the advantage that the run of the two wire beltsnot only extends in a direction with regard to the overall height but,to some extent, is also of contrary design, and therefore the absoluteoverall height, in particular in the case of a rebuild, is reducedconsiderably. Furthermore, by arranging the flowbox at an angle thatruns downward relative to the imaginary second horizontal plane, noincrease in height is achieved, that is to say the flowbox does notincrease the overall height of the twin-wire former, since as far as itscomponents are concerned it is not oriented upward. In addition, onaccount of the deflection, the forming fibrous web is guided on anS-shaped path at an angle relative to an Imaginary horizontal plane.

[0007] In further refinement of the first twin-wire former according tothe invention, it is proposed that the upper vertex of the seconddeflection device be located at least 50 mm, preferably, at least 100mm, in particular at least 200 mm, above the lower vertex of the firstdeflection device, and that the angle between the flowbox and the secondimaginary horizontal plane assume a value between 0° and 45°, preferablybetween 0° and 30°.

[0008] In the case of a second twin-wire former of the type mentioned atthe beginning, this object is achieved, according to the invention, inthat after the first deflection device, the two wire belts run upward atan angle relative to an imaginary second horizontal plane, in that afelt removes the forming fibrous web from the wire belt at a pickuppoint which is located above the lower vertex of the first deflectiondevice, and in that the pickup point is followed by a press unit, inwhich the forming fibrous web is guided first through a first,preferably double-felted press nip with a first press roll and a secondpress roll, after the first press nip is guided, with one of the felts,around the first press roll, is then transferred to a non-felted pressroll in a second press nip and then runs through at least one furthersingle-side-felted press nip.

[0009] In the case of this second twin-wire former according to theinvention, as well, the result is the advantages mentioned in the caseof the first embodiment. In addition, the position of the pickup pointensures that the latter does not contribute to an increase in theoverall height, in particular in the case of a rebuild, but is locatedin the vertical area of the upstream twin-wire former that determinesthe overall height.

[0010] In further refinement of the second twin-wire former according tothe invention, it is proposed that the pickup point be located at least50 mm, preferably at least 100 mm, in particular at least 200 mm, abovethe lower vertex of the first deflection device.

[0011] According to the invention, the angle at which, after thedeflection device, the two wire belts run upward relative to animaginary second horizontal plane assumes a value between 10° and 90°,preferably between 25° and 40°, the desired achievement of the reductionin overall height being assisted positively.

[0012] In a further advantageous refinement of the invention, it isproposed that isobaric dewatering elements, as they are known, bearranged between the first deflection device and a separating device,between which the forming fibrous web runs, enclosed between the twowire belts. Therefore, for the forming fibrous web, the achievement ofthe best possible formation, that is to say the most uniform possiblefiber distribution is ensured, and this with the greatest possibledewatering performance and with the lowest possible energy consumptionduring the web formation operation. Advantageously, at least onestationary isobaric dewatering element is arranged on the one wire beltand at least one isobaric dewatering element is arranged on the otherwire belt, and can be set resiliently against the wire belt by means ofa selectable force. The isobaric dewatering elements can therefore beadapted in a straightforward, time-saving and cost-effective way tovarious operating conditions and to various fibrous suspensions.

[0013] Furthermore, the isobaric dewatering elements are designed asplates or plate segments, since these shapes can be produced andoperated cost-effectively.

[0014] In a further embodiment of the invention, provision is made forat least one flat suction element to be arranged after the separatingdevice, acting on the wire belt which carries the forming fibrous web.In this way, the dewatering and formation of the forming fibrous web isadditionally positively assisted.

[0015] In an advantageous embodiment of the invention, provision is madefor a deflection of the wire belt to follow the second deflectiondevice, in such a way that the wire belt subsequently runs downward atan angle of less than 60°, preferably less than 40°, in particular lessthan 25°, relative to an imaginary second vertical plane.

[0016] In an alternative advantageous refinement, the deflection of thewire belt is carried out in such a way that the wire belt subsequentlyruns substantially horizontally, in a further refinement, a furthersheet forming device, preferably a hybrid former, being arranged afterthe second deflection device. The wire belt advantageously runs at least50 mm, preferably at least 100 mm, above the lower vertex of the firstdeflection device.

[0017] The second deflection device is preferably a suction roll, a shoewith foils or a shoe with foils and with applied vacuum, since theseaforementioned elements belong to the prior art, and therefore possessincreased functional reliability and low procurement costs, and possiblyalso low operating costs.

[0018] In a further embodiment of the invention, provision is made forthe distance between the lower vertex of the first deflection device andthe upper vertex of the second deflection device to have a value between1 and 8 m, preferably between 3 and 6 m.

[0019] In this further embodiment, it is again advantageous that theoverall height is reduced in such a way that, in the case of rebuilds,no substantial additional costs (rebuilding costs, overhaul costs,operating costs) arise.

[0020] With regard to constructional and economic aspects, it isadvantageous if the first deflection device is a closed roll, an openroll or an open roll with applied vacuum.

[0021] Furthermore, with regard to constructional and economic aspects,it is advantageous if the separating device is designed as a suctionseparator and/or a vacuum shoe.

[0022] In addition, it is advantageous with regard to constructional andeconomic aspects if the forming roll which, according to the invention,advantageously has a diameter of greater than 1200 mm, preferablygreater than 1635 mm, in particular greater than 1760 mm, is designed asan open roll, and the open forming roll is closed by means of a grilleor honeycomb structure or is a suction roll.

[0023] These elements just mentioned belong to the known prior art, andtherefore possess an increased functional reliability and lowprocurement costs, possibly also low operating costs.

[0024] With regard to a low overall height of the twin-wire former, onthe one hand, and a minimum number of components in the twin-wireformer, on the other hand, it is beneficial if the forming roll has adewatering capacity which has a value of at least 50%, preferably of atleast 65%, of the total dewatering capacity of the twin-wire former. Thecomponents for the remaining dewatering, together with the associatedoverall height, can therefore turn out to be considerably lower than isusual.

[0025] It is technologically advantageous if the dewatering on thedeflection roll is greater than on the other rolls, that is to say theroll diameter of the deflection roll is greater than the roll diameterof the forming roll and/or the roll diameter of the suction roll.

[0026] Both from constructional and from financial aspects, it isadvantageous if the twin-wire former has an overall height in a rangefrom 2 to 8 m, preferably from 3 to 6 m.

[0027] The twin-wire former according to the invention is also very wellsuited to the application in a former rebuild, since in this caseconstructional conditions which are generally present, for example thedimensions of the whole, have to be taken into account and, as a result,the former rebuild should not entail any further space requirement, forexample as a result of an increased overall height of the twin-wireformer to be installed.

[0028] It goes without saying that the features of the inventionmentioned above and still to be explained below can be used not only inthe respectively specified combination but also in other combinations oron their own, without leaving the scope of the invention.

[0029] Further features and advantages of the invention emerge from thesubclaims and the following description of preferred exemplaryembodiments, making reference to the drawing, in which:

[0030]FIG. 1 shows a schematic and section side view of a firstadvantageous embodiment of the twin-wire former according to theinvention;

[0031]FIG. 2 shows a schematic and section side view of a secondadvantageous embodiment of the twin-wire Former according to theinvention; and

[0032] FIGS. 3 to 6 show schematic and section side views of furtheradvantageous embodiments of the twin-wire former according to theinvention.

[0033] The twin-wire former 1 illustrated in schematic and section sideview in FIG. 1 comprises two endless wire belts, namely a lower wire 2and an upper wire 3, which carry a forming fibrous web 4 centrally.These two wire belts 2, 3 together form a twin-wire zone 5, running overa dewatering element 6 in the form of a rotating forming roll 7 in afirst section in the twin-wire zone 5 and together forming a wedge-likeinlet gap 8 which picks up the fibrous suspension directly from aflowbox 9 fitted at an angle δ relative to an imaginary first horizontalplane H1 (“gap former”). The flowbox 9, illustrated schematically, canof course also be equipped as a multi-layer flowbox and/or as a flowboxwith controllable-section dilution water technology (“Module Jet”system). In a second section of the twin-wire zone 5, the two wire belts2, 3 with the fibrous web 4 forming between them run downward over aplurality of dewatering elements 6 (not specifically illustrated), suchas a forming shoe, a plurality of forming foils or a plurality ofisobaric dewatering elements, at an angle α of 10° to 60° relative to animaginary first vertical plane V1. At the end of the second section ofthe twin-wire zone 5, the two wire belts 2, 3 run over a firstdeflection device 10 with a lower vertex 10.SU and then over aseparating device 11 which acts over the machine width and in the areaof which the upper wire 3 is led away from the forming fibrous web 4 andthe lower wire 2. Of course, in the case of a different design of thetwin-wire former 1, it is also possible for the lower wire 2 to beseparated from the forming fibrous web 4 and the upper wire 3. Theseparated upper wire runs on to a guide roll 12 and from there, directlyor indirectly, over further rolls back to the wedge-like inlet gap 8.After the separating device 11, a second deflection device 15 with anupper vertex 15.SO is arranged, and deflects the lower wire 2 whichcarries the forming fibrous web 4. After that, the lower wire 2 togetherwith the forming fibrous web 4 runs over a suction roll 13 to a pickuppoint S_(p) of a pickup roll 14, on which the pickup roll 14 removes thefibrous web 4 from the lower wire 2 and the fibrous web 4 is transportedto further manufacturing stages in the paper, board or tissue machine.The lower wire runs on to a guide roll 12 and from there, indirectlyover further rolls, back to the wedge-like inlet gap 8.

[0034] According to the invention, in the first advantageous embodimentof the twin-wire former 1 according to the invention, provision is thenmade that, after the first deflection device 10, the two wire belts 2, 3run upward at an angle β relative to an imaginary second horizontalplane H2 in such a way that the upper vertex 15.SO of the seconddeflection device 15 is located above the lower vertex 10.SU of thefirst deflection device, and that the angle δ runs downward relative tothe imaginary first horizontal plane H1. In this case, the angle δ runsdownward in the clockwise direction in FIG. 1 in relation to theimaginary first horizontal plane H1.

[0035] Furthermore, the upper vertex 15.SO or the second deflectiondevice 15 is located at least 50 mm, preferably at least 100 mm, inparticular at least 200 mm, above the lower vertex 10.SU of the firstdeflection device 10 and, according to the invention, the angle δassumes a value between 0° and 45°, preferably between 0° and 30°.

[0036] In addition, the angle β, at which the two wire belts 2, 3 runupward relative to an imaginary second horizontal plane H2 after thefirst deflection device 10, assumes a value between 10° and 90°,preferably between 25° and 40°.

[0037] In addition, the invention provides for a deflection of the wirebelt 2 to be carried out at the second deflection device 15 in such away that the wire belt 2 then runs downward at an angle γ of less than60°, preferably less than 40°, in particular less than 25°, relative toan imaginary second vertical plane V2.

[0038] The forming roll 7 in FIG. 1 has a diameter D7 of greater than 1200 mm, preferably greater than 1 635 mm, in particular greater than 1760 mm, and is designed as a suction roll; however, it can also bedesigned as an open roll, it being possible for the open roll in turn tobe closed by means of a grille or honeycomb structure.

[0039] Furthermore, the forming roll 7 has a dewatering capacity whichhas a value of at least 50%, preferably of at least 65%, of the totaldewatering capacity of the twin-wire former.

[0040] The first deflection device 10 is a closed roll 16; however, itcan also be an open roll or an open roll with applied vacuum.Furthermore, in FIG. 1 the separating device 11 is designed as a suctionseparator 17; however, it can also be designed as a vacuum shoe. Thesecond deflection device 14 is designed as a suction roll; however, itcan also be designed as a shoe with foils or a shoe with foils and withapplied vacuum.

[0041] The distance A between the lower vertex 10.SU of the firstdeflection device 10 and the upper vertex 15.SO of the second deflectiondevice 15 assumes a value between 1 and 8 m, preferably between 3 and 6m. The twin-wire former 1 preferably assumes an overall height H in arange from 2 to 8 m, preferably from 3 to 6 m.

[0042] The twin-wire former 1 illustrated in schematic and section sideview in FIG. 2 in principle resembles the twin-wire former of FIG. 1;with regard to the further description of the twin-wire former 1,reference is made to the description of FIG. 1. According to theinvention, in the second advantageous embodiment of the twin-wire former1 according to the invention, provision is now made for the two wirebelts 2, 3, after the first deflection device 10, to run upward at anangle β relative to an imaginary second horizontal plane H2, for a felt23 to remove the forming fibrous web 4 from the wire belt 2 at a pickuppoint S_(p), which is located above the lower vertex 10.SU of the firstdeflection device 10, and for the pickup point S_(p) to be followed by apress unit 24, in which the forming fibrous web 4 is guided firstthrough a first, preferably double-felted press nip 25 with a firstpress roll 26 and a second press roll 27, after the first press nip 25is guided, with one of the felts 23, around the first press roll 26, isthen transferred to a non-felted press roll 29 in a second press nip 28,and then runs through at least one further single-side-felted press nip30, which is formed by the non-felted press roll 29 and a suction-roll31

[0043] Furthermore, the invention further provides for the pickup pointS_(p) to be located at least 50 mm, preferably at least 100 mm, inparticular at least 200 mm, above the lower vertex 10.SU of the firstdeflection device 10.

[0044] The press unit 24 illustrated in FIG. 2 is taken as an extractfrom the German Published Specification DE 196 54 325 A1 (PC10453 DE).In addition, the German Published Specification DE 197 44 341 A1(PC10623 DE) discloses further-reaching embodiments of an appropriatepress unit. The descriptions of these two aforementioned publishedspecifications are hereby in full made the subject of the presentdescription.

[0045] The press unit 24 in a further embodiment can further be followedby at least one further press unit which is not illustrated but isincluded in the prior art, the combination of individual press unitsbeing possible. The design of the press unit 24 is therefore notrestricted to the design of the same illustrated and described.

[0046] The angle δ runs downward in the counterclockwise direction inrelation to the imaginary first horizontal plane H1 in FIG. 2.

[0047] A further advantageous embodiment of the twin-wire former 1according to the invention is illustrated in schematic and section sideview in FIG. 3. This twin-wire former 1 possesses substantially the sameconstruction with regard to the twin-wire zone 5 as the twin-wire formerof FIG. 1.

[0048] According to the invention, however, isobaric dewatering elements18, 19, as they are known, are arranged between the first deflectiondevice 10 and the separating device 11 of this twin-wire former 1,between which the forming fibrous web 4 runs, enclosed between the twowire belts 2, 3. Isobaric dewatering elements 18 of this type aredescribed in the German Published Specification DE 197 33 316 A1(PB10569 DE) of the Applicant; the content of this aforementionedpublished specification is hereby made the subject of this description.Arranged on the upper wire 3 is a stationary isobaric dewatering element18, and at least one isobaric dewatering element 19 is arranged on thelower wire 2 and can be set resiliently against the lower wire 2 bymeans of a selectable force. It goes without saying that the isobaricdewatering elements 18, 19 can also act on the wire belts 2, 3 in theconverse arrangement. The isobaric dewatering elements 18, 19 aredesigned as plates or plate segments.

[0049] Furthermore, three flat suction elements 20 are arranged afterthe separating device 11 and act on the lower wire 2, which carries theforming fibrous web 4.

[0050] A further advantageous embodiment of the twin-wire former 1according to the invention is illustrated in schematic and section sideview in FIG. 4. This twin-wire former 1 has substantially the sameconstruction with regard to the twin-wire zone 5 as the twin-wire formerof FIG. 1.

[0051] According to the invention, the second deflection device 15 isdesigned as a shoe 21. The deflection is carried out in such a way thatthe lower wire 2 subsequently runs substantially horizontally. Arrangedafter the second deflection device 15 is a further sheet forming device22, which produces a further fibrous web 4.1. The two fibrous webs 4,4.1 are couched by means of known devices and transported to furthermanufacturing stages in the paper, board or tissue machine. Since thefurther sheet forming device is designed as a former belonging to theknown prior art, preferably a hybrid former, it will not be discussedspecifically; instead, reference is made to the known prior art.

[0052] A further advantageous embodiment of the twin-wire former 1according to the invention is shown in schematic and section side viewin FIG. 5.

[0053] As distinct from the other figures, according to the invention,the angle β assumes a value of 90°, so that the twin-wire zone 5 runsvertically upward after the first deflection device 10. This results inthe advantage of improved removal of water without rewetting and withoutthe use of vacuum. After the separation of the wires, the lower wire 2,together with the forming fibrous web 4, is guided over a suction roll13 into a horizontal position. The lower wire 2 together with theforming fibrous web 4 then runs over three flat suction elements 20,which act on the lower wire 2, which carries the forming fibrous web 4.

[0054] The twin-wire former 1 illustrated in schematic and section sideview in FIG. 6 is designed as a hybrid former, known per se, the upperwire 3 of the hybrid former simultaneously forming the fourdrinier wireof a top-fitted fourdrinier wire former with a top fitted hybrid former.With regard to the S-shaped web guidance and the fitting of dewateringelements 6, in particular of isobaric dewatering elements, reference ismade to the above embodiments.

[0055] In summary, it is to be recorded that the invention provides atwin-wire former of the type mentioned at the beginning of which theoverall height is reduced in such a way that, in the case of rebuilds,no significant additional costs (rebuilding costs, overhaul costs,operating costs) arise, and which permit complete secondary dewateringat relatively high machine speeds. List of reference symbols  1Twin-wire former  2 Lower wire (wire belt)  3 Upper wire (wire belt)  4,4.1 Fibrous web  5 Twin-wire zone  6 Dewatering element  7 Forming roll 8 Inlet gap  9 Flowbox 10 First deflection device 11 Separating device12 Guide roll 13 Suction roll 14 Pickup roll 15 Second deflection device16 Roll 17 Suction separator 18, 19 Isobaric dewatering element 20 Flatsuction element 21 Shoe 22 Sheet forming device 23 Felt S_(p) Pickuppoint 24 Press unit 25 Press nip (preferably double-felted) 26 Firstpress roll 27 Second press roll 28 Second press nip 29 Press roll(nonfelted) 30 Press nip (reited or one side) 31 Suction roll A DistanceD7, D13, D15 Roll diameter H Overall height H1 First horizontal plane H2Second horizontal plane 10.SU Lower vertex 15.SO Upper vertex V1 Firstvertical plane V2 Second vertical plane α, β, γ, δ Angle

1. A twin-wire former (1) for producing a fibrous web (4), in particulara paper, board or tissue web, from a fibrous stock suspension, havingthe following features: a) two endless wire belts (lower wire (2) andupper wire (3)) together form a twin-wire zone (5); b) in a firstsection of the twin-wire zone (5), in which the two wire belts (2, 3)run over a dewatering element in the form of a rotating forming roll(7), the two wire belts (2, 3) together form a wedge-like inlet gap (8)which picks up the fibrous stock suspension directly from a flowbox (9)fitted at an angle (δ) relative to an imaginary first horizontal plane(H1) (“gap former”); c) in a second section of the twin-wire zone (5),the two wire belts (2, 3) with the fibrous web (4) forming between themrun downward over further dewatering elements (6) at an angle (α) of 10°to 60° relative to an imaginary first vertical plane (V1); d) at the endof the second section of the twin-wire zone (5), the two wire belts (2,3) run over a first deflection device (10) with a lower vertex (10.SU)and then over at least one separating device (11) which acts over themachine width and in the area of which one of the wire belts (2, 3) isled away from the forming fibrous web (4) and the other wire belt (2,3); e) a second deflection device (15) with an upper vertex (15.SO) isarranged after the separating device (11) and deflects the wire belt (2)that carries the forming fibrous web (4); characterized f) in that afterthe first deflection device (10), the two wire belts (2, 3) run upwardat an angle (β) relative to an imaginary second horizontal plane (H2) insuch a way that the upper vertex (15.SO) of the second deflection device(15) is located above the lower vertex (10.SU) of the first deflectiondevice (10), and g) in that the angle (δ) runs downward relative to theimaginary first horizontal plan (H1).
 2. The twin-wire former (1) asclaimed in claim 1, characterized in that the upper vertex (15.SO) ofthe second deflection device (15) is located at least 50 mm, preferablyat least 100 mm, in particular at least 200 mm, above the lower vertex(10.SU) of the first deflection device (10).
 3. The twin-wire former (1)as claimed in claim 1 or 2, characterized in that the angle (δ) assumesa value between 0° and 45°, preferably between 0° and 30°.
 4. Thetwin-wire former (1) according to the preamble of claim 1, characterizedf) in that after the first deflection device (10), the two wire belts(2, 3) run upward at an angle (β) relative to an imaginary secondhorizontal plane (H2), g) in that a felt (23) removes the formingfibrous web (4) from the wire belt (2) at a pickup point (S_(p)), whichis located above the lower vertex (10.SU) of the first deflection device(10), and h) in that the pickup point (S_(p)) is followed by a pressunit (24), in which the forming fibrous web (4) is guided first througha first, preferably double-felted press nip (25) with a first press roll(26) and a second press roll (27), after the first press nip (25) isguided, with one of the felts (23), around the first press roll (26), isthen transferred to a non-felted press roll (29) in a second press nip(28) and then runs through at least one further single-side-felted pressnip (30).
 5. The twin-wire former (1) as claimed in claim 4,characterized in that the pickup point (S_(p)) is located at least 50mm, preferably at least 100 mm, in particular at least 200 mm, above thelower vertex (10.SU) of the first deflection device (10).
 6. Thetwin-wire former (1) as claimed in one of the preceding claims,characterized in that the angle (β), at which the two wire belts (2, 3)run upward in relation to an imaginary second horizontal plane (H2)after the first deflection device (10), assumes a value between 10° and90°, preferably between 25° and 40°.
 7. The twin-wire former (1) asclaimed in one of the preceding claims, characterized in that isobaricdewatering elements (18, 19), as they are known, are arranged betweenthe first deflection device (10) and the separating device (11), betweenwhich the forming fibrous web (4) runs, enclosed between the two wirebelts (2, 3).
 8. The twin-wire former (1) as claimed in claim 7,characterized in that at least one stationary isobaric dewateringelement (18) is arranged on the one wire belt (2, 3), and at least oneisobaric dewatering element (19) is arranged on the other wire belt (2,3) and can be set resiliently against the wire belt (2, 3) by means of aselectable force.
 9. The twin-wire former (1) as claimed in claim 7 or8, characterized in that the isobaric dewatering elements (18, 19) aredesigned as plates or as plate segments.
 10. The twin-wire former (1) asclaimed in one of the preceding claims, characterized in that after theseparating device (11), there is arranged at least one flat suctionelement (20), which acts on the wire belt (2) which carries the formingfibrous web (4).
 11. The twin-wire former (1) as claimed in one of thepreceding claims, characterized in that at the second deflection device(15), deflection of the wire belt (2) is carried out in such a way thatthe wire belt (2) subsequently runs downward at an angle (γ) less than60°, preferably less than 40°, in particular less than 25°, relative toan imaginary second vertical plane (V2).
 12. The twin-wire former (1) asclaimed in one of claims 1 to 10, characterized in that at the seconddeflection device (15), deflection of the wire belt (2) is carried outin such a way that the wire belt (2) subsequently runs substantiallyhorizontally.
 13. The twin-wire former (1) as claimed in claim 12,characterized in that the wire belt (2) runs over the lower vertex(10.SU) of the first deflection device (10).
 14. The twin-wire former(1) as claimed in claim 13, characterized in that the wire belt (2) runsat least 50 mm, preferably at least 100 mm, above the lower vertex(10.SU) of the first deflection device (10).
 15. The twin-wire former(1) as claimed in one of the preceding claims, characterized in that afurther sheet forming device (22), preferably a hybrid former, isarranged after the second deflection device (15).
 16. The twin-wireformer (1) as claimed in one of the preceding claims, characterized inthat the second deflection device (15) is a suction roll (13), a shoe(21) with foils or a shoe with foils and with applied vacuum.
 17. Thetwin-wire former (1) as claimed in one of the preceding claims,characterized in that the distance (A) between the lower vertex (10.SU)of the first deflection device (10) and the upper vertex (15.SO) of thesecond deflection device (15) assumes a value between 1 and 8 m,preferably between 3 and 6 m.
 18. The twin-wire former (1) as claimed inone of the preceding claims, characterized in that the first deflectiondevice (10) is a closed roll (16), an open roll or an open roll withapplied vacuum.
 19. The twin-wire former (1) as claimed in one of thepreceding claims, characterized in that the separating device (11) isdesigned as a suction separator (17) and/or as a vacuum shoe.
 20. Thetwin-wire former (1) as claimed in one of the preceding claims,characterized in that the forming roll (7) has a diameter (D7) ofgreater than 1200 mm, preferably greater than 1635 mm, in particulargreater than 1760 mm.
 21. The twin-wire former (1) as claimed in one ofthe preceding claims, characterized in that the forming roll (7) has adewatering capacity which has a value of at least 50%, preferably of atleast 65%, of the total dewatering capacity of the twin-wire former (1).22. The twin-wire former (1) as claimed in one of the preceding claims,characterized in that the forming roll (7) is designed as an open roll.23. The twin-wire former (1) as claimed in claim 22, characterized inthat the open forming roll (7) is closed by means of a grille orhoneycomb structure.
 24. The twin-wire former (1) as claimed in claim22, characterized in that the open forming roll (7) is a suction roll.25. The twin-wire former (1) as claimed in one of the preceding claims,characterized in that the roll diameter (D16) of the deflection roll(16) is greater than the roll diameter (D7) of the forming roll (7)and/or the roll diameter (D13) of the suction roll (13).
 26. Thetwin-wire former (1) as claimed in one of the preceding claims,characterized in that it has an overall height (H) in a range from 2 to8 m, preferably from 3 to 6 m.
 27. Use of the twin-wire former (1) asclaimed in one of the preceding claims, in particular in a formerrebuild.